Pump

ABSTRACT

A centrifugal pump having a screw-type suction inducer located in the inlet passage and having a dual-stage pumping section.

United States Patent 1 1 1111 3,751,178 Paugh et a1. 1 Aug. 7,1973

[54] PUMP 1,137,704 4/1915 Dake 415/52 3,435,771 4/1969 Ri 1e 415/143 [751 lnvemms James Paugh, f Mass-i 3,626,694 12/1971 (5 1516 415 143 Theodore J. Pollarl, Brooklyn, Conn. 1

[73] Assignee: Warren Pumps, lnc., Warren, Mass.

. Primary Examiner-C. .1. Husar [22] Filed Attorney-Norman S. Blodgett [21] Appl. No.2 186,909

152] U.S. Cl. 415/56, 415/143 151 1111.01. F0ld 1/12 1571 ABSTRACT [58] Field of Search 415/56-58, 74, 83, 143

A centrifugal pump having a screw-type suction in- [56] References Cited ducer located in the inlet passage and having a dual- UN1TED ST-ATES PATENTS Stage Pumping Section 2,984,189 5/1961 Jekat 415/74 7 3 Claims, 3 Drawing Figures Pmmw 1W5 3751.178

sum 1 or 3 James J. Paugl) Theodore J. Pogq NTORS ATTORNEY PATENIEM 7 SHEET 3 0F 3 FIG. 3.

1 PUMP BACKGROUND OF THE INVENTION In the operation of.centrifugal pumps, one of the common problems is the introduction of the fluid to be pumped into the inlet side of the pump, particularly in starting up. In a large installation, it may be economical to maintain the flow into the inlet side of the pump or to prime the pump by use of a supplementary independent pump. Such an independent pump with its own drive is, of course, expensive and, in anything but very large installations, is not economically feasible. One alternative is to use a different type of pump, but there are situations where a centrifugal pump is called for, because no other type of pump will serve the'purpose. Because of the difficulty of causing adequate flow on the suction side of the centrifugal pump, it has often been necessary to use more pump capacity than is really necessary. The result is again an economic one and, in the past, the installation of centrifugal pumps to satisfy a certain capacity has always been unduly ex.

pensive. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the invention to provide a centrifugal pump which maintains adequate flow of fluid to be pumped to the inlet side without the use of auxiliary pumps.

Another object of the invention is the provision of a centrifugal pump having an inexpensive suction inducer which serves to reduce the required suction head on the pump.

A further object of the invention is the provision of asuction inducer which can be useful in modifying existing centrifugal pumps to reduce their required suction head.

A still further object of the invention is to provide a centrifugal pump having a suction inducer which is simple in construction and which is capable of a long life of useful service.

With these and other objects in view, as will be ap- FIG. 1 is a perspective view of a centrifugal pump embodying the principles of the present invention,

FIG. 2 is a front elevational view of the pump with portions broken away along the line II--II of FIG. 1, and

FIG. 3 is a vertical sectional view of the pump in the portion not broken away in FIG. 2, the section being taken on the line Il-II of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1, wherein are best shown the general features of the invention, the pump, indicated generally by the reference numeral 10, is shown as having a housing 11 mounted on a base 12. The housing I] encloses, in the version of the invention shown in FIG. 1, two elements enclosed in a first portion 13 and a second portion 14. The element enclosed in the first portion 13 is a steam turbine which is not part of the pres- .ent invention but shares the same shaft as the element enclosed in the second portion 14. Thepump is provided with a lubrication system as well as relief valves and the like which are common to centrifugal pumps and which form no part of the present invention.

Evident also in FIG. 1 is the fact that the second portion 14 is provided with an inlet passage 15 and an outlet passage 16. These passages are provided in the usual way with flanged fittings to permit the pump to be conparent to those skilled in the art, the invention resides SUMMARY OF THE INVENTION In general, the invention consists of a centrifugal pump having a housing and having a shaft rotatably mounted in the housing. The housing has an inlet passage coaxial of the shaft and an outlet passage at a right angle to the axis of the shaft. A centrifugal rotor is mounted on the shaft to receive a fluid from the inlet passage and introduce it under pressure into the outlet passage. A suction inducer lies between the inlet passage and the centrifugal rotor to encourage the flow of fluid through the inlet passage to the rotor.

More specifically, the suction inducer consists of a screw mounted axially on the shaft and having a lead which varies from a short lead facing outwardly of the inlet passage to along lead where it lies adjacent the centrifugal rotor.

BRIEF DESCRIPTION OF THE DRAWINGS The character of the invention, however, may be best understood by reference to one of its structural forms, as illustrated by the accompanying drawings, in which:

nected into a hydraulic system.

Referring now to FIG. 2, it can be seen that a shaft 17 is mounted in suitable bearings 18 and 19. The bearing 19, incidentally, carries a thrust portion to absorb any thrust forces on the shaft 17. At one end of the shaft I7 it is provided with a timing gear 21 by which it is attached to a timing mechanism which regulates the rate of rotation. Included in the first portion 13 is a steam turbine for driving the shaft, which turbine consists of a rotor 22 mounted on the shaft 17 and buckets 23 formed in the first portion I3 of the housing 11. Suitable provisions are made for introducing steam to the rotor and the buckets to drive the shaft 17.

In FIG. 3, it can be seen that the second section 14 contains a centrifugal pump including a centrifugal rotor suitably mounted on and keyed to the shaft 17. The rotor is provided with a curved surface which is provided by a passage 25 and which is adapted to receive fluid from the inlet passage 15 and to introduce it into the outlet passage 16. Fluid leaving the passage 25 is diffused by an annular surface '26 formed in a ring 27 mounted in the housing coaxially of and surround ing the periphery of the centrifugal rotor 24. The passage 26 leads radially through the ring 27 to a shroud 29 containing a reversing passage 28. The reversing passage carries the fluid back to a point adjacent the shaft 17 and introduces it once more to another passage 31 formed in the centrifugal rotor. This passage extends axially and then radially and introduces the fluid directly into the outlet passage 16.

Fastened to the end of the shaft 17 is a suction inducer 32 having a main body 33 which is screwed to the end of the shaft 17 and which is of a general bullet shape having its pointed end directed into the inlet passage 15. Its surface blends smoothly into the surface of the passage 25. Extending outwardly from the main body 33 of the suction inducer is a helical vane or screw 34. This screw has a lead which varies from a short lead (low angle) where it lies in the inlet passage 15 to a long lead (high angle) where it lies adjacent the entrance to the passage 26 in the rotor 25. Surrounding the screw is a shroud 35 which is carried in a suitable recess formed in the housing 11 and which has an inner tapered surface 36 which constitutes substantially a continuation of the inlet passage 15. It should be noted that the screw 34 has its outer edge adjacent the surface 35 of the shroud and that it, too, is tapered in the axial direction. In other words, the suction inducer not only contains a variation in lead, as has been described above, but also in the effective diameter of the screw. The screw 34 has, therefore, a rather complex surface that defies description in terms of commonly-known geometric surfaces. it can best be described by the following chart which shows the pitch of the helix at various angles of wrap, starting with wrap at the outer end (in the inlet Angle of Wrap Pitch inl360 0 0 The operation of the invention will now be readily understood in view of the above description. Live steam under pressure is introduced into the first portion 13 and serves to rotate the turbine contained therein to drive the shaft 17. Introduction of steam is regulated in the usual way through the timing gear 21, so as to maintain the rate of rotation of the shaft at a predetermined value commensurate with the most-efficient operation of the centrifugal pump. The rotation of the shaft 17 causes rotation of the centrifugal rotor 24, thus causing flow of fluid from the inlet passage 15 through the passages in the rotor 24 to the outlet passage 16. The use of the ring 27 and its passage 26 combined with the shroud 29 and its reversing passage 28 and with the passage 31 in the centrifugal rotor 25 constitute a two-stage centrifugal pump. Because of the high efficiency and effectiveness of such a pump, difficulty has been experienced in the past in supplying sufficient fluid from the inlet passage 15 to the entrance to the passage 26 in the rotor, i.e., cavitation takes place. For that purpose, the suction inducer 32 of the present invention picks up fluid in the entrance passage 15 and drives it with considerable velocity and pressure into the passage 25. The use of the varying lead means that the fluid is picked up with small velocity and driven through the shroud 35 at high velocity into the passage 25.

It can be seen, then, that the use of the present invention leads to a number of advantages in pump operation. it reduces the suction head required to prevent the cavitation experienced in the conventional impeller. The variable pitch of the suction inducer 32 permits a better hydraulic mating with the impeller, thereby improving suction characteristics without reducing pump efficiency. The two-stage construction of the impeller gives certain advantages over the use of two separate impellers. There is a shorter overhang, re-- sulting in less space, lighter weight, and less shaft deflection. In addition, lower speeds are required to produce a high head (pressure) resulting in less N.P.S.H.

required. (suction pressure) to prevent cavitation.

There are lower disc friction losses, since there are only two rotating shrouds adjacent to a stationary wall; in

the prior art multistage pumps, there are two rotating shrouds for each stage, and the disc friction losses are most significant in high speed equipment (greater than 7,500 rpm). Furthermore, the present invention gives simplified disassembly and maintenance. All parts are removable from the suction headside, thus permitting servicing without dismantling the driver; there are also fewer parts to service.

It is obvious that minor changes may be made in the form and construction of the invention without departing from the material spirit thereof. It is not, however, desired to confine the invention to the exact form herein shown and described, but it is desired to include all such as properly come within the scope claimed.

The invention having been thus described, what is claimed as new and desired to secure by Letters Patent 1. A pump, cormprising:

a. a housing,

b. a shaft rotatably mounted in the housing, the housing having an inlet passage coaxial of the shaft and an outlet passage extending at a right angle to the axis of the shaft.

c. a centrifugal rotor mounted on the shaft and formed to receive fluid from the inlet passage and introduce it into the outlet passage, and

d. a suction inducer having a screw with edges and mounted on the shaft and lying between the inlet passage and the centrifugal rotor in a shroud having a bore with a surface which is tapered with the small diameter directed toward the rotor, the edges of the screw lying close to the surface of the bore. A pump, comprising:

a housing,

. a shaft rotatably mounted in the housing, the housing having an inlet passage coaxial of the shaft and an outlet passage extending at a right angle to the axis of the shaft,

c. a centrifugal rotor mounted on the shaft and formed to receive fluid from the inlet passage and introduce it into the outlet passage, the rotor having a primary passage leading first axially and then radially of the shaft, wherein a ring is mounted in the housing and has a reversing passage which leads from the primary passage radially inwardly to adjacent the shaft, and wherein the rotor has a secondary passage that leads first axially and then radially from the reversing passage to the outlet passage, and

d. a suction inducer mounted on the shaft and lying between the inlet passage and the centrifugal rotor.

3. A pump, comprising:

a. a housing,

b. a shaft rotatably mounted in the housing, the housing having an inlet passage coaxial of the shaft and an outlet passage extending at a right angle to the axis of the shaft,

c. a centrifugal rotor mounted on the shaft and formed to receive fluid from the inlet passage and introduce it into the outlet passage, and

d. a suction inducer mounted on the shaft and lying between the inlet passage and the centrifugal rotor, and is provided with a screw having a pitch which varies from a small pitch at the end directed toward the inlet'passage and a large pitch at the'end directed toward the rotor.

* i. i i i 

1. A pump, cormprising: a. a housing, b. a shaft rotatably mounted in the housing, the housing having an inlet passage coaxial of the shaft and an outlet passage extending at a right angle to the axis of the shaft. c. a centrifugal rotor mounted on the shaft and formed to receive fluid from the inlet passage and introduce it into the outlet passage, and d. a suction inducer having a screw with Edges and mounted on the shaft and lying between the inlet passage and the centrifugal rotor in a shroud having a bore with a surface which is tapered with the small diameter directed toward the rotor, the edges of the screw lying close to the surface of the bore.
 2. A pump, comprising: a. a housing, b. a shaft rotatably mounted in the housing, the housing having an inlet passage coaxial of the shaft and an outlet passage extending at a right angle to the axis of the shaft, c. a centrifugal rotor mounted on the shaft and formed to receive fluid from the inlet passage and introduce it into the outlet passage, the rotor having a primary passage leading first axially and then radially of the shaft, wherein a ring is mounted in the housing and has a reversing passage which leads from the primary passage radially inwardly to adjacent the shaft, and wherein the rotor has a secondary passage that leads first axially and then radially from the reversing passage to the outlet passage, and d. a suction inducer mounted on the shaft and lying between the inlet passage and the centrifugal rotor.
 3. A pump, comprising: a. a housing, b. a shaft rotatably mounted in the housing, the housing having an inlet passage coaxial of the shaft and an outlet passage extending at a right angle to the axis of the shaft, c. a centrifugal rotor mounted on the shaft and formed to receive fluid from the inlet passage and introduce it into the outlet passage, and d. a suction inducer mounted on the shaft and lying between the inlet passage and the centrifugal rotor, and is provided with a screw having a pitch which varies from a small pitch at the end directed toward the inlet passage and a large pitch at the end directed toward the rotor. 